man sysctl.conf
Я добавил в sysctl.conf "net.ipv4.conf.all.mc_forwarding = 1"
После перзагрузки
:/# /sbin/sysctl -a|grep forwarding
.....
net.ipv4.conf.all.forwarding = 0
net.ipv4.conf.all.mc_forwarding = 0
net.ipv4.conf.default.mc_forwarding = 0
net.ipv4.conf.lo.mc_forwarding = 0
net.ipv4.conf.eth0.mc_forwarding = 0